High Voltage Electron Diffraction and Computer Graphics of Heavy Meromyosin Crystals

Abstract

It is well known that myosin is one of main proteins which has a central role in muscle contraction and cell motility. Myosin molecule is composed of heavy and light meromyosin (HMM and LMM). Heavy meromyosin has two heads and each head contains an ATP hydrolyzing site and an actin binding site (1, 2). Heavy meromyosin (HMM) can be divided by proteolytic reagents into subfragment-1 and subfragment-2 (SI and S2). It is important to know on the mechanism of muscle contraction whether any conformational change of myosin heads and/or actin filaments occur or not. Therefore, three dimensional reconstructions from electron micrographs of the reconstituted actin containing filaments with myosin, heavy meromyosin or SI have been investigated (3–7). However, it is difficult to separate actin and myosin with a high spacial resolution in a complexed pattern. Thus, it is necessary to assign intra- and intermolecular structures of myosin heads in detail. Many approaches were undertaken to obtain structural information of the myosin heads using electron microscopy (8–11), X-ray scattering (12) and Hydrodynamic techniques (13). The size and shape of myosin heads are, however, slightly different with different analysis.